If you have to go longer in between changes, say when you are out, etc. use a hemp or hemp fleece insert. this will hold a TON more than MF. Also, snap the onesie just in the middle - that will leave the other fabric away from the diaper;s edge,

Don't feel bad mama, you learn as you go. It's much harder to learn when the people around you are telling you the wrong things. You found us and you're in good hands now.
If it doesn't kill you to do so I second cutting off the bottom of the onesie to make a shirt.